Stationary engine coolant circuit

ABSTRACT

The present invention has a waste heat recovery device ( 37 ) that supplies engine waste heat by way of engine coolant; a radiator ( 18 ) that dissipates engine waste heat by way of engine coolant; an exhaust gas heat exchanger ( 33 ) that supplies engine waste heat from exhaust gas to engine coolant; and a coolant pump ( 32 ) that causes engine coolant to circulate. Furthermore, the constitution is such that pressure drop equipment ( 34 ) is arranged upstream with respect to a coolant pump suction region ( 32   b ); a restrictor is arranged in a communication passage ( 50 ) between a coolant pump suction region and a region ( 20 ) vented to atmosphere; a location upstream with respect to the pressure drop equipment is made to communicate with the region vented to atmosphere; and the region vented to atmosphere is made capable of being kept in communication with atmosphere.

TECHNICAL FIELD

The present invention relates to a coolant circuit for a stationaryengine having a waste heat recovery device such as might be employed ina GHP (gas heat pump) or a cogeneration system.

BACKGROUND ART

Disclosed conventionally as a coolant circuit for a stationary enginehaving a waste heat recovery device, in the context of an engine coolantcircuit having a waste heat recovery device, is a constitution in whicha coolant pump suction region communicates with a region vented toatmosphere (see, for example, Patent Reference No. 1).

That is, the engine coolant circuit described in Patent Reference No. 1is equipped with a waste heat recovery device constituted such that aradiator is in contact with an outdoor heat exchanger. Moreover, theinlet region side of the coolant pump is connected to a reserve tank,and the coolant pump suction port communicates with atmosphere by way ofa vent hole provided at the reserve tank.

PRIOR ART REFERENCES Patent References

PATENT REFERENCE NO. 1: Japanese Patent Application Publication KokaiNo. H09-88602 (1997)

SUMMARY OF INVENTION Problem to be Solved by Invention

With the constitution of the engine coolant circuit of theaforementioned Patent Reference No. 1, pressure at the coolant pumpsuction region will be more or less equal to head pressure at thereserve tank, and so long as the coolant pump is not arranged at alocation higher than the reserve tank, it will not be possible to setthe pressure at the pump suction region so as to be the same or lessthan the head pressure.

However, an engine coolant circuit having a waste heat recovery deviceis equipped with an exhaust gas heat exchanger for causing engine heatto be absorbed by engine coolant from exhaust gases prior to supply ofengine waste heat by way of engine coolant at the waste heat recoverydevice. Because it heats engine coolant, there is a possibility thatsuch an exhaust gas heat exchanger might be treated as a type of boiler.Where the exhaust gas heat exchanger is thus treated as a boiler, therewill be a desire to keep the pressure of that engine coolant as low aspossible.

The present application therefore addresses the problem of making itpossible, in the context of an engine coolant circuit having a wasteheat recovery device, to adjust pressure as required at a coolant pumpsuction region, which is where pressure in the circuit is lowest, so asto be any desired pressure that is the same or less than head pressure,for the purpose of setting pressure within the coolant circuit of anexhaust gas heat exchanger or the like so as to be a prescribedpressure.

Means for Solving Problem

The present invention, being conceived in order to solve the aforesaidproblem, is a stationary engine coolant circuit having a waste heatrecovery device that supplies engine waste heat by way of enginecoolant; a radiator that dissipates engine waste heat by way of enginecoolant; an exhaust gas heat exchanger that supplies engine waste heatfrom exhaust gas to engine coolant; and a coolant pump that causesengine coolant to circulate, the constitution being such that a coolantpump suction region is made to communicate with a region vented toatmosphere; a location upstream with respect to the pressure dropequipment is made to communicate with the region vented to atmosphere; arestrictor is arranged in a communication passage between the regionvented to atmosphere and the location upstream with respect to thepressure drop equipment; and the region vented to atmosphere is capableof being kept in communication with atmosphere.

In such present invention, the pressure drop from the pressure dropequipment makes it possible to cause pressure at the coolant pumpsuction region to be lower than head pressure. Furthermore, by adjustingflow rate at the restrictor in the passage communicating with the regionvented to atmosphere, it is possible to adjust pressure so as to be anydesired pressure within a range from a negative pressure belowatmospheric pressure to the head pressure at the region vented toatmosphere. This being the case, it is possible to set pressure withinthe coolant circuit to be a prescribed pressure while maintaining enginecoolant flow rate so as to be equal to (pump suction regionpressure+pump discharge pressure+pressure drop to measurement location).

The exhaust gas heat exchanger in the aforesaid present invention isarranged at a location that is at a discharge side of the coolant pumpand that is downstream with respect to the engine. In such presentinvention, it is possible to cause pressure at the inlet port of theexhaust gas heat exchanger to be (pump suction region pressure+pumpdischarge pressure+pressure drop across flow passages within engine),this being lower than (pump suction region pressure+pump dischargepressure) by an amount corresponding to (pressure drop across flowpassages within engine).

In the aforesaid present invention, a motor-driven three-way valvehaving an adjustable opening is arranged at a region where a radiatordownstream passage and a waste heat recovery device downstream passagemeet. In such present invention, because a motor-driven three-way valveis arranged at a location in the engine coolant circuit at which coolanttemperature is lowest, heat resistance of the motor-driven three-wayvalve is improved. Note that the motor-driven three-way valvecorresponds to one example of the aforesaid pressure drop equipment.

In the aforesaid present invention, a thermostat is arranged at adischarge side of the coolant pump; the waste heat recovery device isarranged at a passage on a high-temperature side of said thermostat; anda radiator is arranged at a location downstream with respect to thewaste heat recovery device. In such present invention, when enginecoolant temperature is at or above the thermostat setpoint temperature,all coolant flow will be directed to the waste heat recovery device.This being the case, when calculating the amount of heat supplied fromthe engine coolant, as compared with a constitution in which there iscontrol of divided flow with respect to the waste heat recovery deviceand the radiator, calculation is simplified to the extent that there isno need to take engine coolant flow ratio into account.

In the aforesaid present invention, the region vented to atmosphere isconstituted such that a vent pipe is provided at an upper region of acoolant tank, the coolant pump suction region and at least one of eitherthe exhaust gas heat exchanger or the radiator being made to communicatewith a watersealed region of the coolant tank. In such presentinvention, because a location in the coolant circuit at which there ishigh probability of air pocket formation is vented to atmosphere by wayof a watersealed region, it is possible to definitively carry outgas-liquid separation on bubbles so that only engine coolant is returnedto the circuit.

In the aforesaid present invention, the constitution is such that two ofthe coolant tanks are provided; the vent pipe being provided at one ofthe tanks; and further, an air pocket region at one of the tanks beingmade to communicate with an air pocket region at the other tank; thecoolant pump suction region and at least one of either the exhaust gasheat exchanger or the radiator being made to communicate with awatersealed region at the other tank; a watersealed region at one of thetanks being made to communicate with a watersealed region at the othertank; and a bottom of the tank provided with the vent pipe beingarranged at the same height or elevation as a bottom of the other tank.In such present invention, because a constitution is adopted in whichtwo tanks are provided, it is possible to divide these in terms offunction such that one serves as reserve tank while the other serves toallow gas-liquid separation of high-temperature bubbles that rise upfrom within the circuit, permitting prevention of elevated reservecoolant temperature as a result of gas-liquid separation.

BENEFIT OF INVENTION

In the present invention, because the pressure drop from the pressuredrop equipment and adjustment of the opening at the restrictor make itpossible to adjust the pressure at the coolant pump suction region so asto be any desired pressure that is the same or less than head pressure,this can be set as required so as to be the same or lower thanatmospheric pressure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram showing an engine coolant circuit in acogeneration apparatus associated with one embodiment of the presentinvention.

FIG. 2 is a front perspective view showing the entirety of samecogeneration apparatus.

FIG. 3 is a rear perspective view showing the entirety of samecogeneration apparatus.

FIG. 4 is a schematic drawing of a coolant tank.

EMBODIMENTS FOR CARRYING OUT INVENTION

Below, embodiments of the present invention are described with referenceto the drawings.

In the present embodiment, description is carried out in terms of asituation in which the present invention is applied to a cogenerationapparatus 1. Note that cogeneration apparatus 1 refers to a system,where a commercial electric power subsystem of an external commercialpower supply and an electric power generation subsystem of an electricgenerator are connected to an electric power delivery subsystem thatdelivers electric power to electric power consuming equipment (load),that meets the electric power demand of said load, that recovers wasteheat generated in accompaniment to electric power generation, and thatutilizes said recovered heat.

FIG. 1 shows a circuit diagram of an engine coolant circuit in thecogeneration apparatus, FIG. 2 shows a front perspective view of sameapparatus, and FIG. 3 shows a rear perspective view of same apparatus.

As shown in FIG. 2 and FIG. 3, cogeneration apparatus 1 associated withthe present embodiment is equipped with shell 2 serving as enclosure.The interior of this shell 2 is divided vertically into two regions, thelower region comprising engine chamber 3 and equipment housing chamber5, and the upper region comprising radiator chamber 7, intake chamber 8,and exhaust chamber 9.

Arranged within the aforesaid engine chamber 3 there are an engine 10,an electric generator 11 driven by this engine 10, and an oil tank 12storing lubricating oil.

The aforesaid equipment housing chamber 5 is arranged to the side (rightside as shown in FIG. 2) of engine chamber 3. Arranged within equipmenthousing chamber 5 there are an inverter 14 and a control box 17 equippedwith a control apparatus 16 for controlling engine drive equipment andso forth.

The aforesaid radiator chamber 7 is arranged above equipment housingchamber 5, radiator 18 and coolant tank 20 being arranged within thisradiator chamber 7. Heat-dissipating radiator fan 19, driving of whichis controlled by the aforesaid control apparatus 16, is arranged aboveradiator chamber 7.

Respectively arranged at intake chamber 8 are air cleaner 22 and intakesilencer 23. Arranged at exhaust chamber 9 is exhaust silencer 24.

Next, referring to FIG. 1, the engine coolant circuit will be described.This engine coolant circuit 30 is equipped with coolant pump 32, whichis the drive source for causing circulation of engine coolant. Connectedin order as one proceeds downstream from the discharge side (coolantpump discharge region 32 a) of this coolant pump 32 there are coolantpassages (water jacket) internal to engine 10, exhaust gas heatexchanger 33, and thermostat 35.

Engine 10 might be a stationary gas engine using municipal gas or thelike as fuel, the exhaust system thereof being equipped with theaforesaid exhaust gas heat exchanger 33 and the aforementioned exhaustsilencer 24. Furthermore, engine coolant passing through engine 10 issent to exhaust gas heat exchanger 33, and after heat from exhaust gasis removed therefrom at exhaust gas heat exchanger 33, is made to flowinto thermostat 35 by way of passage 31.

Thermostat 35 is equipped with passage 35 a on the low-temperature sidethereof and passage 35 b on the high-temperature side thereof, thedownstream end of low-temperature passage 35 a being connected to theinlet side (coolant pump suction region 32 b) of coolant pump 32.Furthermore, the downstream end of high-temperature passage 35 b isconnected to liquid-liquid heat exchanger 37 serving as waste heatrecovery device.

Thermostat 35 is such that when temperature of engine coolant is below aprescribed temperature (e.g., when the engine is first started), enginecoolant is made to flow to low-temperature passage 35 a; and such thatwhen engine coolant reaches a temperature that is at or above aprescribed temperature, engine coolant is made to flow tohigh-temperature passage 35 b and liquid-liquid heat exchanger 37.

Liquid-liquid heat exchanger 37 supplies heat removed from enginecoolant to the exterior, supplying heat to water flowing in thesecondary-water side 38 of a hot water supply, for example. Respectivelyprovided at locations upstream and downstream from liquid-liquid heatexchanger 37 are temperature sensors 43, 44 for detecting temperature ofengine coolant.

Engine coolant that has passed through liquid-liquid heat exchanger 37is made to flow to radiator 18 and motor-driven three-way valve 34. Thatis, motor-driven three-way valve 34 comprises a motor valve controlledby the aforesaid control apparatus 16, and has three ports, these beingfirst coolant inlet 34 a, second coolant inlet 34 b, and coolant outlet34 c.

Furthermore, connected to first coolant inlet 34 a is the downstream endof waste heat recovery device downstream passage 39, which extends fromliquid-liquid heat exchanger 37. Moreover, connected to second coolantinlet 34 b is the downstream end of radiator downstream passage 40,which extends from radiator 18. Accordingly, motor-driven three-wayvalve 34 is arranged at a region where waste heat recovery devicedownstream passage 39 and radiator downstream passage 40 meet. Note thatwaste heat recovery device downstream passage 39 is connected by way ofpassage 42 to radiator 18.

Furthermore, coolant outlet 34 c is connected by way of coolant supplypipe 41 to the aforesaid low-temperature passage 35 a.

Motor-driven three-way valve 34 is such that the ratio between thedegree to which first coolant inlet 34 a and second coolant inlet 34 bare opened is capable of being changed (adjustment of opening), theopening ratio being determined in correspondence to the amount of heatexchange occurring at liquid-liquid heat exchanger 37. Specifically,when the amount of heat exchange occurring at liquid-liquid heatexchanger 37 is large, i.e., when the amount of heat being dissipated byengine coolant is large, the degree to which first coolant inlet 34 a isopened will be large; and when the amount of heat exchange occurring atliquid-liquid heat exchanger 37 is small, i.e., when the amount of heatbeing dissipated by engine coolant is small, the degree to which secondcoolant inlet 34 b is opened will be large.

The aforesaid coolant tank 20 comprises two tanks, one tank (reservetank) 20 a being made of synthetic resin, and the other tank (gas-liquidseparation tank) 20 b being made of metal. Connected to the one tank 20a is a vent pipe 48 that is capable of being kept in communication withatmosphere. The bottom of the coolant at the one tank that is providedwith vent pipe 48 is arranged at the same height or elevation as thebottom of the other tank, and moreover, respective air pocket regions atthe one tank 20 a and the other tank 20 b are made to communicate bymeans of communication pipe 46. Furthermore, watersealed regions of thetwo tanks 20 a, 20 b (the portions thereof at which engine coolant isstored) are made to communicate by way of communication pipe 47 whichextends to the respective lower portions of the tanks.

The lower portion of the other tank 20 b is connected by way ofcommunication pipe 45 to the upper portion 18 a of radiator 18.Furthermore, communication pipe 49 is connected between the lowerportion of the other tank 20 b and plumbing (not shown), through whichengine coolant flows, within exhaust gas heat exchanger 33. Radiator 18and exhaust gas heat exchanger 33 are arranged at elevation(s) higherthan engine 10, the reason being that they are locations within thecoolant circuit that are susceptible to formation of air pockets. Bythus providing an air purge circuit leading to a gas-liquid separationtank at location(s) where there is danger of air pocket formation, thisallows gas-liquid separation to be carried out so that only enginecoolant is returned for intake by coolant pump 32.

Moreover, restrictors 60 and 61 are provided so as to prevent excessiveflow of engine coolant to communication pipes 45 and 49 and so as toadjust pressure at the inlet side of coolant pump 32 to any desiredpressure that is the same or less than head pressure.

However, if it should become necessary to drastically reduce pressure atcoolant pump suction region 32 b, the diameters of restrictors 61, 60may be increased, or the restrictors might be removed from communicationpipes 45, 49 and a restrictor 51 might be provided at communicationpassage 50, so as to allow pressure within the circuit to be adjusted toa lower value.

Cogeneration apparatus 1 of the present embodiment having the foregoingconstitution, operation with respect to circulation in the coolantcircuit will next be described.

Upon causing coolant pump 32 to operate, engine coolant discharged fromcoolant pump 32 is supplied to engine 10, its temperature becomingelevated as it cools cylinders and various other locations while passingthrough the interior of engine 10, and it moreover passes throughexhaust gas heat exchanger 33 to arrive at thermostat 35. At thermostat35, when coolant temperature is below a prescribed temperature, enginecoolant is returned to coolant pump 32.

Furthermore, when engine coolant reaches a temperature that is at orabove a prescribed temperature, thermostat 35 causes engine coolant toflow to liquid-liquid heat exchanger 37. Here, in the event that thereis desire for supply of hot water, at liquid-liquid heat exchanger 37,heat from engine coolant is extracted to the exterior as it is used toheat water flowing in the secondary-water side 38 of a hot water supply.Furthermore, the amount of engine coolant flowing to radiator 18 isadjusted in correspondence to the amount of heat exchange occurring atliquid-liquid heat exchanger 37. When the amount of heat exchange islarge, the degree to which first coolant inlet 34 a of motor-driventhree-way valve 34 is opened is greater than the degree to which secondcoolant inlet 34 b thereof is opened, and the amount of coolant flowingthrough waste heat recovery device downstream passage 39 and bypassingradiator 18 is large.

When the amount of heat exchange is small, the degree to which secondcoolant inlet 34 b of motor-driven three-way valve 34 is opened isgreater than the degree to which second coolant inlet 34 a thereof isopened, and the amount of coolant flowing to radiator 18 is large.

Furthermore, the passage which goes from coolant pump suction region 32b, through communication passage 50 and coolant tank 20, to vent pipe 48constitutes a line vented to atmosphere; and because both thecommunication pipe 49 from exhaust gas heat exchanger 33 and thecommunication pipe 45 from radiator 18, at which the pressure within thecoolant circuit is higher than at coolant pump suction region 32 b, gothrough restrictors 61, 60 before meeting at coolant tank 20, it ispossible to cause the pressure at coolant pump suction region 32 b to bethe same or less than head pressure.

Furthermore, by providing exhaust gas heat exchanger 33 downstream withrespect to engine 10, this makes it possible to reduce the pressure dropby an amount corresponding to the contribution from engine 10 and thusreduce the pressure acting at exhaust gas heat exchanger 33.

By providing motor-driven three-way valve 34 at the suction location ofthe pump, which is the location within the coolant circuit wheretemperature is lowest, reliability with respect to the part(s) employedfor motor-driven three-way valve 34 is improved. Moreover, with improvedreliability it becomes possible to use motor-driven three-way valve 34over a long period and achieve cost reduction.

When engine coolant temperature increases and the state of thermostat 35becomes such that the high-temperature side thereof is opened, becauseall flow constantly goes through liquid-liquid heat exchanger 37, itwill be possible to calculate the amount of heat exchange occurring atliquid-liquid heat exchanger 37 by detecting the change in watertemperature at temperature sensor 43 at the inlet side of liquid-liquidheat exchanger 37 versus temperature sensor 44 at the outlet sidethereof. This being the case, as compared with the situation in whichradiator 18 and liquid-liquid heat exchanger 37 are arranged inparalleled fashion, because computation of the amount of heat exchangeno longer requires a flowmeter at the passage leading to liquid-liquidheat exchanger 37, cost reduction is made possible. Alternatively, ascompared with use of the ratio of opening relative to liquid-liquid heatexchanger 37 at motor-driven three-way valve 34 to calculate flow rateto liquid-liquid heat exchanger 37, computational load is reduced.

Also, an air purge circuit leading to a gas-liquid separation tank isprovided at location(s) where there is danger of air pocket formation,such as at exhaust gas heat exchanger 33 and radiator 18. This being thecase, bubbles mixed with engine coolant at exhaust gas heat exchanger 33and radiator 18 are, as shown at FIG. 4, made to pass throughcommunication pipe 49 and communication pipe 45, to flow into the othertank 20 b. Moreover, only air passes through communication pipe 46 andenters the one tank 20 a, the air traveling through vent pipe 48 to bedischarged to atmosphere. Thus, because the constitution is such thatgas-liquid separation is carried out, with only engine coolant beingreturned to the circuit interior, it is possible to reduce the size ofradiator 18, and it is also possible to prevent cavitation at coolantpump 32. Note that engine coolant within the one tank 20 a moves asappropriate to the interior of the other tank 20 b by way ofcommunication pipe 47.

By carrying out gas-liquid separation of high-temperature bubbles at theother tank (gas-liquid separation tank) 20 b, which is different fromthe one tank (reserve tank) 20 a, it is possible to prevent increase inwater temperature at the reserve tank. In addition, because increase inwater temperature is prevented thereat, the reserve tank may bemanufactured easily and cheaply from synthetic resin.

The present invention is not limited to the foregoing embodiment. Forexample, as indicated by the imaginary line at FIG. 1, it is possiblefor the bottom of the coolant at the one tank that is provided with ventpipe 48 to be arranged so as to be at higher elevation than the bottomof the other tank. In such case, it will be possible to more easilycause engine coolant within the one tank 20 a to move to the interior ofthe other tank 20 b by way of communication pipe 47.

Furthermore, it is also possible to employ the present invention in anengine-driven heat pump. The present invention may be embodied in a widevariety of forms other than those presented herein without departingfrom the spirit or essential characteristics thereof. The foregoingembodiments and working examples, therefore, are in all respects merelyillustrative and are not to be construed in limiting fashion. The scopeof the present invention being as indicated by the claims, it is not tobe constrained in any way whatsoever by the body of the specification.All modifications and changes within the range of equivalents of theclaims are, moreover, within the scope of the present invention.

Moreover, this application claims priority based on Patent ApplicationNo. 2008-121521 filed in Japan on 7 May 2008. The content thereof ishereby incorporated in the present application by reference.

POTENTIAL INDUSTRIAL USE

The stationary engine coolant circuit associated with the presentinvention is effective as a coolant circuit for a stationary enginehaving a waste heat recovery device, and is particularly suited to usein a GHP (gas heat pump) or a cogeneration system.

EXPLANATION OF REFERENCE NUMERALS

-   1 Cogeneration apparatus-   2 Shell-   10 Engine-   18 Radiator-   20 Coolant tank-   20 a The one tank-   20 b The other tank-   30 Engine coolant circuit-   32 Coolant pump-   32 a Coolant pump discharge region-   32 b Coolant pump suction region-   33 Exhaust gas heat exchanger-   34 Motor-driven three-way valve-   35 Thermostat-   37 Liquid-liquid heat exchanger (waste heat recovery device)-   39 Waste heat recovery device downstream passage-   40 Radiator downstream passage-   41 Coolant supply pipe-   42 Passage-   43 Temperature sensor-   44 Temperature sensor-   45 Communication pipe-   46 Communication pipe-   47 Communication pipe-   48 Vent pipe-   49 Communication pipe-   50 Communication passage-   51 Restrictor-   60 Restrictor-   61 Restrictor

1. A stationary engine coolant circuit having a waste heat recoverydevice that supplies engine waste heat by way of engine coolant; aradiator that dissipates engine waste heat by way of engine coolant; anexhaust gas heat exchanger that supplies engine waste heat from exhaustgas to engine coolant; and a coolant pump that causes engine coolant tocirculate, the stationary engine coolant circuit being characterized inthat it is constituted such that pressure drop equipment is arrangedupstream with respect to a coolant pump suction region, and two of thecoolant tanks are provided; a vent pipe capable of being kept incommunication with atmosphere being provided at one of the tanks; andfurther, an air pocket region at the one tank being made to communicatewith an air pocket region at the other tank; a location upstream withrespect to the pressure drop equipment being made to communicate with awatersealed region at the other tank; and a restrictor being arranged ina coupling passage between the location upstream with respect to thepressure drop equipment and the watersealed region.
 2. A stationaryengine coolant circuit according to claim 1, the stationary enginecoolant circuit being characterized in that the exhaust gas heatexchanger is arranged at a location that is at a discharge side of thecoolant pump and that is downstream with respect to the engine.
 3. Astationary engine coolant circuit according to claim 1, the stationaryengine coolant circuit being characterized in that a motor-driventhree-way valve having an adjustable opening is arranged at a regionwhere a radiator downstream passage and a waste heat recovery devicedownstream passage meet.
 4. A stationary engine coolant circuitaccording to claim 1, the stationary engine coolant circuit beingcharacterized in that a thermostat is arranged at a discharge side ofthe coolant pump; the waste heat recovery device is arranged at apassage on a high-temperature side of said thermostat; and a radiator isarranged at a location downstream with respect to the waste heatrecovery device.
 5. (canceled)
 6. (canceled)